1. Field of the Invention
This invention relates to techniques of preparing products, such as mineral wool felts, which by reason of their resilience are of low volumetric mass and are advantageously compressed during storage and transportation.
2. Description of the Prior Art
In the conventional packaging of lightweight felts a lightweight felt is rolled onto itself and thereby compressed. In this way, cylindrical rolls are formed, the stability of which is guaranteed by the wrapping which is normally a sheet of paper or a sheet of polymeric material.
With regard to bulk, if it is advantageous to compress the felt considerably, the rate of compression chosen must also take into account the product's capacity to resume its thickness when used. The qualities of felts, particularly their insulating qualities, indeed depend upon their thickness. Experience shows that to ensure a satisfactory restoration of thickness when the product is no longer compressed, it is necessary to limit the rates of compression imposed.
The best possible way of rolling up these products is to use a method which, by ensuring uniform compression over the entire length, makes it possible to work at the highest acceptable rate of compression without compromising the quality of the procuct. Also, rolling up the felt guarantees the quality of the product in a packaging which offers the minimum of bulk.
Various means have been proposed in order to arrive at this result.
Typically, the felt is conveyed into a space defined by two conveyor belts and a compression roller. These belts and this roller entrain the felt into a rotational movement terminating in its being wound onto itself. The compression roller may move in such a way as progressively to enlarge the space in which the felt is being rolled up.
In order to arrive at a uniform compression of the felt, it is necessary for the pressure exerted by the compression roller to grow with the number of turns of felt rolled. The law of increase in pressure to be applied depends on numerous parameters.
Hitherto, the means used for increasing the pressure exerted have not been entirely satisfactory.
In the typical conventional construction, the increase in pressure exerted results directly from the increase in the "diameter" of the felt rolled up. For example, the compression roller is disposed on the end of a movable arm. The roll of felt, as it grows, pushes back the compression roller. A pneumatic jack fixed on the arm carrying the compression roller exercises a reaction which tends to oppose the movement of the arm. The pressure in the pneumatic jack which is transmitted through the arm and the compression roller to the felt while the felt is being rolled up is all the greater as the displacement of the compression roller becomes greater.
Even when such means are refined, it is not possible in practice satisfactorily to follow the progression necessary to ensure a uniform rate of compression of the felt over its entire length. Typically, it is found more often than not that compression is much higher in the center of the roll in comparison with that which is exerted on parts situated at the periphery. Having regard to the necessity of the roll resuming its thickness, the tendency is to reduce the compression over the whole of the roll. Consequently, the prepared products are either less long or more bulky than would be necessary if one were perfectly to control the handling and preparation of the felt.
On the other hand, an additional difficulty results from the need, in certain installations, to treat varied products having characteristic features, particularly vis-a-vis compression, which may be vastly different from one another. Under these conditions, at every change in production, it is necessary to modify the mechanical arrangements, which necessitates relatively long and delicate adjustment.